Package org.opt4j.operator.crossover

Class CrossoverDoubleBLX

java.lang.Object

org.opt4j.operator.crossover.CrossoverDouble

org.opt4j.operator.crossover.CrossoverDoubleElementwise

org.opt4j.operator.crossover.CrossoverDoubleBLX

All Implemented Interfaces:

Operator<DoubleGenotype>, Crossover<DoubleGenotype>

public class CrossoverDoubleBLX
extends CrossoverDoubleElementwise

The CrossoverDoubleBLX is an implementation of the blend crossover operator proposed by Eshelman and Schaffer, 1993.

The BLX crossover is applied element-wise. For two double values y and x (assuming y > x one offspring value is created in the uniform interval [x-(y-x)*alpha;y+(y-x)*alpha].

If alpha is set to 0, the operator creates a random solution between x and y. Values greater zero allow offspring that is apart from the interval between x and y. The authors report best performance with alpha = 0.5 which is then called the BLX-0.5 operator.

Field Summary

Fields

Modifier and Type	Field	Description
protected final double	alpha

Fields inherited from class org.opt4j.operator.crossover.CrossoverDouble

normalize, random

Constructor Summary

Constructors

Constructor	Description
CrossoverDoubleBLX(double alpha, NormalizeDouble normalize, Rand random)	Constructs a CrossoverDoubleBLX with an alpha value, an NormalizeDouble operator, and a random number generator.

Method Summary

Modifier and Type	Method	Description
Pair<Double>	crossover(double x, double y)	Performs a crossover with two double values.
protected double	next(double lo, double hi)	Calculates a random value in the interval [lo-(hi-lo)*alpha;hi+(hi-lo)*alpha].

Methods inherited from class org.opt4j.operator.crossover.CrossoverDoubleElementwise

crossover

Methods inherited from class org.opt4j.operator.crossover.CrossoverDouble

crossover

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

alpha

protected final double alpha

Constructor Details

CrossoverDoubleBLX

@Inject
public CrossoverDoubleBLX(double alpha,
 NormalizeDouble normalize,
 Rand random)

Constructs a CrossoverDoubleBLX with an alpha value, an NormalizeDouble operator, and a random number generator.

Parameters:

alpha - the alpha value

normalize - the normalize operator

random - the random number generator

Method Details

crossover

public Pair<Double> crossover(double x,
 double y)

Description copied from class: CrossoverDoubleElementwise

Performs a crossover with two double values.

Specified by:

crossover in class CrossoverDoubleElementwise

Parameters:

x - the first value

y - the second value

Returns:

the resulting values

next

protected double next(double lo,
 double hi)

Calculates a random value in the interval [lo-(hi-lo)*alpha;hi+(hi-lo)*alpha].

Parameters:

lo - the smaller double value

hi - the bigger double value

Returns:

a random value in the interval